Individual circuit boards are commonly tested by placing each board on a test fixture coupled to an automatic testing machine. The test fixture usually includes a planar member, generally referred to as a translator board. On a first surface of the translator board is a first plurality of connecting members arrayed to each make contact with a separate one of a plurality of nodes on the circuit board into which test signals are to be launched by the testing machine and from which responses are recovered for analysis. On a second, opposing surface of the translator member is a plurality of second connecting members arrayed in spaced rows. Each first connecting member is electrically coupled to a corresponding second connecting member. In this way, each node of the array on the circuit board is effectively "translated" to a separate one of the second connecting members.
Each of the rows of second connecting members on the translator board is electrically connected by way of a separate paddle card to a corresponding channel card connected to a separate channel of the testing machine. In the past the paddle cards have been passive, electrically conducting members, each typically taking the form of a conventional circuit board of FR-4 or the like.
Traditionally, most automatic testing machines have been designed to launch TTL-level signals into, and to recover TTL-level responses from, the circuit board under test. In the event that the circuit board under test has one or more nodes that are designed to receive and/or generate signals at a logic level other than the TTL-level, such as CMOS, ECL, DCL, DTL or DECL levels, for example, then a signal level translator is required. In the past, active logic devices (i.e., electronic circuits) were mounted directly on the translator board for translating any non-TTL level signal and/or response to a TTL level as required.
The disadvantage of this approach is that each translator board is custom-designed in order to achieve the necessary translation between the nodes on the circuit board under test and the spaced rows of second connecting members on the translator board second surface. Given its custom nature, fabrication of each translator board using mass production techniques is impractical, thus making translator board fabrication time-consuming and costly. Adding active logic to the translator board to perform whatever signal-level translation may be required only serves to increase the complexity of the translator board, thus increasing its fabrication time and cost.
Thus, there is a need for a test fixture which accomplishes any required signal-level translation at a far lower complexity and cost as compared to the prior art.